Wondering about this gets you about as far as wondering why people try taking on towers at lvl1, or people buying the xp upgrades when we're either 20 or close to it.

Personally though, I'll sometimes set it off on random if I'm full on mana or am heading back to base, just because it doesn't cost me anything. Using it as a finisher rather than an opener might be something that's not immediately apparent when you're more focused on other matters.

   The answer is:  Why not?  Maybe a teammate will TP to you.  Maybe creeps will help keep some of the dmg on you going into a battle.  Maybe it'll make you back off a tower a little earlier.  If you don't need the mana it's rarely a bad idea to put dmg on an enemy.

I'll do it if I have a high mana regen item.  Sure, they might just heal it back before they get into combat, but they might also be down 100+ HP when they fight too, and I've survived fights with less then 100 HP.

Other then that, its the annoying factor.  I'll usually "pick on" one player with my random snipes, hoping to piss them off or bait them into mines/gang fights.  Usually it doesnt work, but occasionally it does.  Either way I dont see a problem with it*.

*This is usually late game, when I  am running back to a crystal, or my gear is going to completely regen that in no time.

It you aren't able to go for a kill shot because you just used a random snipe, then you are need to be a little more conservative.  If you are not harassing someone with regulus and you have at least lev 1 snipe, you are being too conservative.  Get the damage in whenever possible and try to control the enemies' movements (ex if you can't contain an enemy player and 1 is running towards a flag, use a snipe to make them nervous and drive them back, etc, even if there is no chance for a kill).   Obviously, not much point in sniping an oak with bishops at low level snipe unless they are in combat or about to be in. 

Anyway, the bottom line is, if you can (and it doesn't cause you to miss a kill shot or have to run back to base too quickly), snipe away.  Just pick the best strategic target at that time. 

its usually a stupid idea if the opponent has enough health regen (or monks or whatever) so it won't actually succeed in harassing like it was intended. its almost always best to just wait and save the mana and time the snipes for when your ally is actually fighting another DG. 

if its a map with vey high regen (Exile or Leviathan, for example) then you can probably afford to waste the mana on it. in that case though i wouldn't think of targetting a Demigod, it would just get regenned off. really you ought to be taking potshots at enemy towers if you can get away with it. 

I mainly play regulus now. Mostly because I am the best person with the group of people I play with in laying mines at the right time. I don't do a conventional build, but it is fairly effective (I am over %50 with regulus). When I play against a regulus that does random snipe, I find my team usually wins.

Snipe is most useful when a battle is about to begin to start the other team with a disadvantage, or to finish off someone who is running. At level one the snipe only does 400 damage, and most classes heal that back naturally before the next snipe. Once you get the 800 damage snipe, most demigods have 4000+ HP so the random snipe is again ineffective.

there is no good reason, even playing as someone squishy like tb 1000 damage out of combat is nothing, and your health regen is going to take care of it like it wasnt there to begin with. its more of an indication of your oponents skill, as soon as you get hit by the first random snipe you can say "thank god, this reg isnt going to be a threat at all this game"

Against a General, don't bother unless it's for tracking device. Against an Assassin, it's good. Most won't head back to base after just one hit, and so they're running around with less health, making it quite a bit easier to take them down later.

I've been playing with the Staff of Renewal lately, and others don't seem to expect the rapidfire snipes and mines everywhere.

Always, always follow up with another Snipe. 5 in a row begins to hurt a bit.